Varieties of interbody fusion devices are widely used following partial or total discectomies for stabilization of the spine at the site. Some stabilization devices are anchored to the pedicles. With several systems, the use of the pedicles requires screws or other anchoring devices that occupy significant space and involve muscle dissection and associated work-time for implantation. Nerve root injuries are a well-known potential complication of placement of screws in the pedicles.
The inter-spinous (“ISP”) process devices are designed to increase the ISP height, thereby increasing the sagittal cross-sectional area of the foramen, where the nerve roots pass away out of the spine. It is thought that these devices may also unload the facet joints, and perhaps the intervertebral disc. They may limit spinal extension. This backward bending position may be painful for patients with spinal stenosis because it reduces the space available for the nerve roots in the exiting foraminal openings.
In addition to ISP implants, ISP fixation devices are also common to fix adjacent spinous processes to each other to stabilize the spinal motion-segment as an adjunct to spinal fusion. Current systems include spinous process plates that are fixed with adjacent spinous processes sandwiched therebetween.